NS_ERROR_FAILURE with absent property

I trying to capture pageLoad event in progressListener, in onLocationChange i check URI of fresh page, and in case URI = about:blank i got

Error: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIURI.host]

As i understand this URI don't have host at all.

How can i check that host is available without raw parsing and exception catching? I开发者_运维知识库s there any conventional way to check that atribute is present?

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Your best bet is to filter certain protocols (filter on scheme). It's best to use a whitelist in this case of the protocols you care about.

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In general there's no way to know for sure without doing a try/catch, but currently an nsIStandardURL is the only sort of URI that will have a host.

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When I faced this problem my solution was: To indicate an observer flag aWebProgress.NOTIFY_LOCATION

aWebProgress.addProgressListener(this.listener, aWebProgress.NOTIFY_LOCATION);

Before I had aWebProgress.NOTIFY_LOCATION and there was an exception you desc